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| Description: In the absence of effector (upper left) the ligand-binding site (L) is unoccupied, and a transcriptional antiterminator (AT) can form. Alternatively, if the riboswitch functions at the level of translation (lower left), a region containing the Shine-Dalgarno sequence (SD) is not paired with its complement (anti-SD, or ASD), and translation can occur. In the presence of an effector, the mRNA tertiary structure can change to pair the antiterminator sequence with its complement (AAT), allowing a terminator loop (T) to form, leading to transcriptional termination (upper right). Alternatively (lower right), binding the ligand permits the Shine-Dalgarno sequence to pair with its complement (ASD) so that translation cannot initiate. Picture Stats: Views: 392 Filesize: 25.57kB Height: 252 Width: 318 Source: https://biology-forums.com/index.php?action=gallery;sa=view;id=35156 |